diff options
Diffstat (limited to 'pylint/checkers/base.py')
| -rw-r--r-- | pylint/checkers/base.py | 52 |
1 files changed, 51 insertions, 1 deletions
diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py index c9e8b75..f368a65 100644 --- a/pylint/checkers/base.py +++ b/pylint/checkers/base.py @@ -62,6 +62,14 @@ REVERSED_PROTOCOL_METHOD = '__reversed__' SEQUENCE_PROTOCOL_METHODS = ('__getitem__', '__len__') REVERSED_METHODS = (SEQUENCE_PROTOCOL_METHODS, (REVERSED_PROTOCOL_METHOD, )) +TYPECHECK_COMPARISON_OPERATORS = frozenset(('is', 'is not', '==', + '!=', 'in', 'not in')) +LITERAL_NODE_TYPES = (astroid.Const, astroid.Dict, astroid.List, astroid.Set) +UNITTEST_CASE = 'unittest.case' +if sys.version_info >= (3, 0): + TYPE_QNAME = 'builtins.type' +else: + TYPE_QNAME = '__builtin__.type' PY33 = sys.version_info >= (3, 3) PY3K = sys.version_info >= (3, 0) @@ -1455,6 +1463,14 @@ class LambdaForComprehensionChecker(_BasicChecker): self.add_message('deprecated-lambda', node=node) +def _is_one_arg_pos_call(call): + """Is this a call with exactly 1 argument, + where that argument is positional? + """ + return (isinstance(call, astroid.Call) + and len(call.args) == 1 and not call.keywords) + + class ComparisonChecker(_BasicChecker): """Checks for comparisons @@ -1472,6 +1488,13 @@ class ComparisonChecker(_BasicChecker): 'Used when the constant is placed on the left side' 'of a comparison. It is usually clearer in intent to ' 'place it in the right hand side of the comparison.'), + 'C0123': ('Using type() instead of isinstance() for a typecheck.', + 'unidiomatic-typecheck', + 'The idiomatic way to perform an explicit typecheck in ' + 'Python is to use isinstance(x, Y) rather than ' + 'type(x) == Y, type(x) is Y. Though there are unusual ' + 'situations where these give different results.', + {'old_names': [('W0154', 'unidiomatic-typecheck')]}), } def _check_singleton_comparison(self, singleton, root_node): @@ -1498,8 +1521,10 @@ class ComparisonChecker(_BasicChecker): self.add_message('misplaced-comparison-constant', node=node, args=(suggestion,)) - @check_messages('singleton-comparison', 'misplaced-comparison-constant') + @check_messages('singleton-comparison', 'misplaced-comparison-constant', + 'unidiomatic-typecheck') def visit_compare(self, node): + self._check_unidiomatic_typecheck(node) # NOTE: this checker only works with binary comparisons like 'x == 42' # but not 'x == y == 42' if len(node.ops) != 1: @@ -1516,6 +1541,31 @@ class ComparisonChecker(_BasicChecker): elif isinstance(right, astroid.Const): self._check_singleton_comparison(right, node) + def _check_unidiomatic_typecheck(self, node): + operator, right = node.ops[0] + if operator in TYPECHECK_COMPARISON_OPERATORS: + left = node.left + if _is_one_arg_pos_call(left): + self._check_type_x_is_y(node, left, operator, right) + + def _check_type_x_is_y(self, node, left, operator, right): + """Check for expressions like type(x) == Y.""" + left_func = helpers.safe_infer(left.func) + if not (isinstance(left_func, astroid.ClassDef) + and left_func.qname() == TYPE_QNAME): + return + + if operator in ('is', 'is not') and _is_one_arg_pos_call(right): + right_func = helpers.safe_infer(right.func) + if (isinstance(right_func, astroid.ClassDef) + and right_func.qname() == TYPE_QNAME): + # type(x) == type(a) + right_arg = helpers.safe_infer(right.args[0]) + if not isinstance(right_arg, LITERAL_NODE_TYPES): + # not e.g. type(x) == type([]) + return + self.add_message('unidiomatic-typecheck', node=node) + def register(linter): """required method to auto register this checker""" |